1. Field of the Invention
The present invention relates to a method for the manufacture of 1,1-diacetoxyethane (ethylidene diacetate) from methylacetate and/or dimethyl ether. 2. Background
Abbreviations: The following abbreviations are utilized herein: EDA for ethylidene diacetate; MA for methyl acetate; and DME for dimethyl ether.
Ethylidene diacetate (EDA) is a valuable chemical which can be used as such (e.g. as solvent for chemical processes or compounds) as well as starting material for chemicals such as vinyl acetate or acetic acid anhydride.
It has been suggested in British specification No. 1,538,782, published Jan. 28, 1979, that EDA can be produced by carbonylation of methyl acetate (MA) and/or dimethyl ether (DME) in the presence of a Group VIII noble metal catalyst, a bromide or chloride and a promoter in the substantial absence of water. The reaction conditions as described in the above-mentioned specification lead, however, to the production of EDA with low selectivity. Moreover, a variety of by-products such as acetic acid anhydride and acetaldehyde are formed together with considerably more than the stoichiometrically expected amount of the less valuable acetic acid.
The presence of a promoter is considered essential for the process described in the aforementioned British patent specification. This is illustrated by the experiments described in Examples 5 and 8, respectively, wherein in the absence of a promoter no reaction products appear to have been formed at all under otherwise similar conditions.
Surprisingly, it has now been found that EDA can be produced with a good selectivity under mild process conditions when a sulphur-containing polar solvent is used. It should be noted that the sulphur-containing compounds used as solvent in the process according to the present invention cannot be considered as promoters, since their presence in promoter quantities in MA (the preferred solvent/reactant according to British patent specification No. 1,538,782) leads to an even lower selectivity than the promoters mentioned in the British patent specification. The use of other polar, non-sulphur-containing solvents such as acetonitrile and dimethyl formamide only leads to the production of acetic acid and various by-products.